1. Field of the Invention
The present invention relates to a data mirroring method, and more particularly to a data mirroring method and an information processing system for smoothly mirroring data in backing up data.
2. Related Art
A conventional data mirroring method is disclosed for example in U.S. Pat. No. 5,742,792, entitled xe2x80x9cRemote Data Mirroringxe2x80x9d, and is described with reference to FIG. 5.
In FIG. 5, a site A is composed of a host A12 and a main data storage system 14 and a remote site B remotely controlled is composed of a host B52 and an auxiliary data storage system.
The main data storage system 14 is composed of a controller 16 and a storage unit 20, and the auxiliary data storage system 46 is composed of a controller 44 and a storage unit 48.
And the controllers 16 and 44 are respectively composed of channel controllers 26 and 54 for sending and receiving data to and from the hosts 12 and 52, data controllers 32 and 68 for controlling internal buses 38 and 70, caches 28 and 64 for temporarily writing and reading data, communication controllers 36 and 42 for sending and receiving data between the site A and the remote site B, and disk controllers 30 and 66 for sending and receiving data to and from the storage units 20 and 48.
In the above-mentioned composition, in case of writing data from the host A12, mirroring modes of three kinds are shown. A first mode is called a synchronous mode, in which data to be stored are stored from the host A12 through the channel controller 26 into the cache 28, are stored through the disk controller 30 into the storage unit 20, are stored through the communication controllers 36 and 42 into the cache 64, are stored through the disk controller 66 into the storage unit 48, and after the data storing has been finished, a data completion notice is sent from the data controller 68 to the host A12 through the communication controllers 42 and 36 and through the channel controller 26. In this case, the reliability of storing data is high, but since the data completion notice is late, the host A12 results in being restrained in operation for a long time.
Next, a second mode is called a semi-synchronous mode, in which data to be stored are first sent from the host A12 to the channel controller 26 together with a write command, and when the cache 28 has received all the data the channel controller 26 sends a write command completion notice to the host A12. After this, the data to stored are stored into the storage unit 20, are stored into the cache 64 through the communication controllers 36 and 42, and are stored into the storage unit 48 through the disk controller 66. Then, after the cache 64 has received all the data, the data controller 68 sends a reception response to the data controller 32 through the communication controllers 42 and 36, and a series of data storing operations are finished. In this semi-synchronous mode, since a completion response is sent to the host A12 before a data reception response comes from the remote site B, the host A12 is made faster by a time for processing data transfer and response between the sites than the synchronous mode. From the viewpoint of data reliability, however, there is the possibility of losing data when the data are sent and received between the controllers 16 and 44.
Next, a third mode is called an adaptive copy (hereinafter, referred to as an adaptive copy) mode, in which data to be stored are first sent from the host A12 to the channel controller 26 together with a write command, and when the cache 28 has received all the data the channel controller 26 sends a write command completion notice to the host A12. The data controller 32 stores a fact that this completion notice has been performed into a queue, and if the next command has been issued from the host A12, so long as there is a free space in the storage area of the queue, the data controller 32 sends a completion notice of the said next command to the host A12. After this, at a proper timing the data controller 32 stores the data registered at the queue into the storage unit 20 and stores the data into the storage unit 48 through the communication controllers 36 and 42 and through the disk controller 66. Then, after the data controller 68 has received all the data, it sends a reception response to the data controller 32 through the communication controllers 42 and 36. Each time the data controller 32 receives the reception response, it decrements the queue, and at the point of time when the queue becomes zero, a series of write operations are completed. In this adaptive copy mode, since a completion response is sent to the host regardless of data transfer with the remote site B so long as there is a free space in the queue, the response is made faster than the second semi-synchronous mode, the semi-synchronous mode. From the viewpoint of data reliability, however, there is the possibility of losing data when a sequence of data corresponding to the number of items registered at the queue are sent and received.
As described above, in the conventional mirroring modes of three kinds, the system operates in a mode fixed by specifying one of these three modes in advance, and for example, in case that the system is set at the synchronous mode, since a command completion notice cannot be sent to the host so long as no reception response comes from the remote site even if the system is heavily loaded, the system can perform a process only in a speed of the same degree as before and this problem makes a bottleneck of the whole system performance.
And in case that a system administrator attempts to change over a mirroring mode to another mirroring mode during a mirroring operation, since it has to issue a specialized command from a maintenance system accompanying a host or disk system and the intervention is performed manually, the system is most heavily loaded and there is the possibility of losing a timing at which a high-speed operation is required.
The present invention provides a data mirroring method capable of solving the above-mentioned problems, and aims at providing a data mirroring method capable of changing over the mirroring mode among the above-mentioned data mirroring modes of three kinds according to the degrees of burdens on the hosts and the respective controllers.
A data mirroring method of the present invention is a data mirroring method which, in a system provided with a first information processing apparatus composed of a first host and a first disk system for sending and receiving data to and from the first host and a second information processing apparatus composed of a second host and a second disk system, connects the first disk system and the second disk system to each other and makes data common to the first disk system and the second disk system;
said data mirroring method selecting one of data mirroring modes of at least three kinds including a synchronous mode, a semi-synchronous mode and an adaptive copy mode being different in speed of processing the data from one another according to the quantity of operations with the first host.
In a data mirroring method of the present invention, the quantity of operations with the first host is the number of commands received and responded per unit time for sending and receiving data between the first host and the first disk system.
In a data mirroring method of the present invention, the quantity of operations with the first host is the quantity of information received and responded per unit time for sending and receiving data between the first host and the first disk system.
In a data mirroring method of the present invention, the quantity of operations with the first host is related to commands received and responded and commands waiting for being processed out of the commands sent from the first host to the first disk system, and is the sum of values each of which is obtained by multiplying the number of commands fitting in an access range by a correlation coefficient determined by the access range for each command.
In a data mirroring method of the present invention, the quantity of operations with the first host is related to commands received and responded and commands waiting for being processed out of the commands sent from the first host to the first disk system, and is the sum of values each of which is obtained by multiplying the information quantity of data to be processed by the commands fitting in an access range by a correlation coefficient determined by the access range for each command.
A data mirroring method of the present invention compares the sum with the range of the said applicable sum in case of using a data mirroring mode at that point of time which has been determined in advance,
keeps the data mirroring mode as it is when the sum is within the range of the said applicable sum in case of using a data mirroring mode at that point of time which has been determined in advance, and changes over the mirroring mode to a mirroring mode making it possible to display a better performance when the sum becomes larger than the upper limit of the said applicable sum.
A data mirroring method of the present invention compares the sum with the range of the said applicable sum in case of using a data mirroring mode at that point of time which has been determined in advance,
keeps the data mirroring mode as the sum is when it is within the range of the said applicable sum in case of using a data mirroring mode at that point of time which has been determined in advance, and changes over the mirroring mode to a mirroring mode making it possible to display a better performance when the sum becomes larger than the upper limit of the said applicable sum.
An information processing system of the present invention is an information processing system provided with a first information processing apparatus comprising a first host and a first disk system for sending and receiving data to and from the first host, and a second information processing apparatus comprising a second host and a second disk system; wherein the first disk system and the second disk system are connected to each other, data can be made common to the first disk system and the second disk system, and the first disk system is provided with a monitoring controller for monitoring a command related to the first host and selects one of data mirroring modes of at least three kinds including a synchronous mode, a semi-synchronous mode and an adaptive copy mode being different in speed of processing the data from one another according to the quantity of operations with the first host.
In an information processing system of the present invention, the quantity of operations with the first host is the number of commands received and responded per unit time for sending and receiving data between the first host and the first disk system.
In an information processing system of the present invention, the quantity of operations with the first host is the quantity of information received and responded per unit time for sending and receiving data between said first host and said first disk system.
In an information processing system of the present invention, the quantity of operations with the first host is related to commands received and responded and commands waiting for being processed out of the commands sent from the first host to the first disk system, and is the sum of values each of which is obtained by multiplying the number of commands fitting in an access range by a correlation coefficient determined by the access range for each command.
In an information processing system of the present invention, the quantity of operations with the first host is related to commands received and responded and commands waiting for being processed out of the commands sent from the first host to the first disk system, and is the sum of values each of which is obtained by multiplying the information quantity of data to be processed by the commands fitting in an access range by a correlation coefficient determined by the access range for each command.
An information processing system of the present invention compares the sum with the range of the said applicable sum in case of using a data mirroring mode at that point of time which has been determined in advance,
keeps the data mirroring mode as it is when the sum is within the range of the said applicable sum in case of using a data mirroring mode at that point of time which has been determined in advance, and changes over the mirroring mode to a mirroring mode making it possible to display a better performance when the sum becomes larger than the upper limit of the said applicable sum.
A system of the present invention is an information processing system being provided with a site A comprising a host A and a main storage system, and a remote site B remotely controlled comprising a host B and an auxiliary data storage system, wherein;
the main data storage system is provided with a controller A for controlling the said system and a storage unit A,
the auxiliary data storage system is provided with a controller B for controlling the said system and a storage unit B,
the controllers A and B are respectively composed of;
channel controllers A and B for sending and receiving data to and from the hosts A and B,
data controllers A and B for controlling internal buses inside the controllers A and B,
caches A and B for temporarily writing and reading data,
communication controllers A and B for sending and receiving data between the site A and the remote site B, and
disk controllers A and B for sending and receiving data to and from the storage units A and B, and further
the controller A comprises a monitoring controller connected to said channel controller A, said monitoring controller monitoring the number of commands or the quantity of information sent from the host A to the channel controller A when the same memory content is stored in the storage units A and B.
In an information processing system of the present invention, the monitoring controller changes a response mode to the host A according to the number of commands or the information quantity, and
the response modes comprise;
a synchronous mode in which data are sent to the remote site B and a reception response from the remote site B is received by the controller A and then a write comand completion notice is sent to the host A,
a semi-synchronous mode in which after the controller A has received all the data contained in a write command and before it receives a reception response from the remote site B, a completion response is sent to the host A, but before a reception response is received from the remote site B the next write command from the host A is not accepted, and
an adaptive mode in which after the controller A has received all the data contained in a write command and before it receives a reception response from the remote site B, a completion response is sent to the host A, and even before a reception response is received from the remote site B the next write command from the host A is accepted.
In an information processing system of the present invention, the adaptive mode is selected when the number of commands or the information quantity is larger than a first threshold value,
the semi-synchronous mode is selected when it is equal to or less than the first threshold value and larger than a second threshold value, and
the synchronous mode is selected when it is equal to or less than the second threshold value.
In an information processing system of the present invention, the number of commands or the information quantity is related to commands received and responded and commands waiting for being processed out of the commands sent from the first host to the first disk system, and is set as the sum of values each of which is obtained by multiplying the number of commands or the information quantity fitting in an access range by a correlation coefficient determined by the access range for each command.
The present invention provides a data mirroring method which, in a system comprising an information processing apparatus composed of a host and a disk system for sending and receiving data to and from the host which are installed at a certain spot and an information processing apparatus composed of a host and a disk system which are remote in distance from the spot, connects the respective disk systems to each other through no host and copies data from one information apparatus to the other so as to improve the reliability and secure the maintainability of one information processing system and so as to minimize an influence on the performance such as delay of response to a running job or a lowering of processing speed, said data mirroring method being capable of obtaining the optimum performance of a system as a whole by automatically changing over prepared data mirroring methods of three kinds being different in processing speed through monitoring the activity of the hosts.
And describing the present invention with reference to FIG. 1, a write command from a host A100 is received by a host controller A121, and in a similar way a completion response of it is sent from the host controller A121 to the host A100. A state of reception response of the write command is monitored by a write activity detector 125. The degree of congestion of commands (the number of commands received and responded per unit time, a command queuing state, etc.) and the data mirroring mode at that point of time are compared with each other, and in case that it is recognized that the performance may be influenced, the mode is changed over to a mode capable of displaying a better performance. On the contrary, when an influence comes not to exist, the mode is changed over to such a mode as a synchronous mode in which the reliability is considered to be more important. By doing so, it is possible to keep the write performance of the system at a high level regardless of a state of command accessing of the host.
In addition, the mode is changed over to a proper mode within a range where there is no influence on the performances of a disk system and a host, depending upon the relation between the residual quantity of commands to be processed from the host to the disk system as the operation quantity of the host and the weighting of the commands in one of the current data mirroring modes of three kinds.